Chain folding in poly(p-phenylene sulfide): A study of the packing of the adjacent re-entry folds by molecular mechanics

Models of tight isolated folds between adjacent chains of poly(p-phenylene sulfide) have been found for folds in the (020), (200) and (110) planes and optimized by molecular mechanics. Minimizations of the conformational ener gy of the folded chains have given low energy values, mainly for the (110) fold planes. Minimizations of the packing energy of the folded chains in th e crystal for each of the three fold planes have given a low energy value o nly For the folds in the (110) planes. The energy required to fold the chai ns evaluated by our calculations has been compared with the work of fold de rived by experimental measurements and reported in the literature. A possib le model of the crystal growth direction as bilayers along b is also sugges ted.